"What’s Opera, Doc? (1957)—an animated masterpiece which cast Bugs and Elmer Fudd in the roles of Brunhild and Siegfried in a hilariously tweaked adaptation of Richard Wagner’s The Ring of the Nibelung—was the first cartoon short to be inducted into the National Film Registry of the Library of Congress in 1992."

- Encyclopaedia Britannica

“It has been widely praised by many in the animation industry as the greatest animated cartoon that Warner Bros. ever released, and has been ranked as such in the top 50 animated cartoons of all time. In 1992, the Library of Congress deemed it "culturally, historically or aesthetically significant", and selected it for preservation in the National Film Registry, the first cartoon short to receive such honors.”

-Wikipedia